(+)- and (xe2x88x92)-2-cyclododecylpropanol and (+)- and (xe2x88x92)-2-cyclododecylpropionic acid and the preparation and use thereof
The present invention relates to (+)- and (xe2x88x92)-2-cyclododecylpropanol and (+)- and (xe2x88x92)-2-cyclododecylpropionic acid, to salts thereof, and to the preparation and use thereof.
The racemate of 2-cyclododecylpropanol (also called Hydroxyambran(copyright) or Amberwood(copyright)) is an odorant of the wood and ambergris class, which is becoming increasingly important (EP-B278 384). A process for its preparation, described in WO 98/55228, is the reaction of cyclodecene in the presence of catalytic amounts of a free-radical initiator with an excess of propionic acid or of a propionic acid derivative and subsequent catalytic hydrogenation of the resulting 2-cyclododecylpropionic acid or of the corresponding 2-cyclododecylpropionic acid derivative respectively.
Neither the two enantiomers of 2-cyclododecylpropionic acid nor of 2-cyclododecylpropanol have hitherto been disclosed in the prior art.
It is an object of the invention to prepare a fragrance of the wood and ambergris class which has a more intensive odor compared with the prior art and which is further notable for improved properties such as staying power, odor threshold value and a low limit of dilution.
We have found that this object is achieved according to the invention by (xe2x88x92)-2-cyclododecylpropanol.
Surprisingly, we have also found that while the (xe2x88x92)-enantiomer is highly suitable as a fragrance, the virtually odorless (+)-enantiomer is advantageously suitable as a fixative for other fragrances. It provides for a long-lasting adhesion, without adversely affecting the intrinsic odor of the adhering fragrance by a strong odor of its own.
The two enantiomers of 2-cyclododecylpropionic acid, the precursor and the intermediate for the preparation of cyclododecylpropanol are prepared by racemate resolution of known racemic 2-cyclododecylpropionic acid by crystallization of the diastereomeric salts using an optically active amine as auxiliary, and subsequent liberation of the respective enantiomer of the acid from the salt, e.g. by reaction with a strongly acidic ion exchanger. For further purification, the crystallization of the diastereomeric salt and the subsequent liberation of the acid can be carried out a number of times. Furthermore, the enantiomerically pure acid can be further purified by recrystallization (Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Volume IV, Allgemeine chemische Methoden, [General chemical methods], Part 2, Georg Thieme Verlag Stuttgart, 1955, pp. 505-532).
The two enantiomers of 2-cyclododecylpropanol are prepared by reduction of the acid function of the corresponding enantiomers of 2-cyclododecylpropionic acid. The reduction can be carried out, for example, by catalytic hydrogenation or using a complex hydride, for example lithium aluminum hydride.
The invention therefore also provides for the use of (+)- or (xe2x88x92)-2-cyclododecylpropionic acid as an intermediate for the preparation of (xe2x88x92)- or (+)-2-cyclododecylpropanol respectively
Surprisingly, the odor of the enantiomers of 2-cyclododecylpropanol is completely different. While the (+)-enantiomer is virtually odorless, the (xe2x88x92)-enantiomer has a considerably stronger odor than the racemic mixture. The odor of racemic 2-cyclododecylpropanol is determined virtually exclusively by the (xe2x88x92)-enantiomer. Although it is known that enantiomers can differ in terms of odor (e.g. (+)-carvone [caraway], (xe2x88x92)-carvone [spearmint], L. Friedman, J. G. Miller, xe2x80x9cOdor Incongruity and Chiralityxe2x80x9d, Science 1971, 172, 1044, cited by G. Ohloff xe2x80x9cRiechstoffe and Geruchsinnxe2x80x9d [Odorants and sense of smell], p.42, Springer-Verlag 1990), the differences are usually qualitative in nature and only pronounced to a greater or lesser extent. The complete discrimination of the odor of the two enantiomers into highly odorous and odorless is extremely rare (cf. G. Ohloff xe2x80x9cRiechstoffe and Geruchsinnxe2x80x9d, p.44, Springer-Verlag 1990) and has hitherto not been described for simple molecules having only one asymmetric center.
It is a particularly advantageous aspect for the use in perfume oils that the (xe2x88x92)-enantiomer is very compatible with all commercially available odorants, for example the classes of cyclic and acyclic terpenes, of aliphatic, cycloaliphatic, aromatic odorants, of phenol derivatives or of heterocycles.